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TVM Errors
==========

TVM may raise errors from Python code, from C++ code reached through the
FFI, or from generated runtime modules.  Error messages usually include
a Python stack trace, and may also include a C++ stack trace when the
error crosses the TVM FFI boundary.

Some errors report invalid user input, unsupported operators, missing
runtime features, or unavailable hardware.  Others report a failed
internal check, usually raised by ``TVM_FFI_ICHECK`` or
``TVM_FFI_THROW`` in C++ code.  Internal check failures often indicate
that TVM reached a state that the implementation did not expect.

What to Check First
-------------------

- Make sure the TVM Python package and native libraries come from the
  same build.  A common symptom of a mismatched environment is importing
  Python files from one checkout while loading ``libtvm`` from another.
- Check that the required runtime is enabled in ``config.cmake``.  For
  example, CUDA tests and CUDA compilation require a TVM build with
  CUDA support enabled.
- Check that the target hardware is available to the process.  GPU
  tests may be skipped or fail if the device is not visible inside the
  current container or environment.
- If the error occurs while importing or converting a model, reduce the
  input to the smallest model, operator, or shape that reproduces the
  issue.

Reporting an Issue
------------------

Search the `Apache TVM Discuss Forum <https://discuss.tvm.apache.org/>`_
and the `TVM issue tracker <https://github.com/apache/tvm/issues>`_
for the exact error message first.  If you do not find an existing
report, include the following details when starting a new discussion or
filing an issue:

- The TVM version or git commit hash.
- The Python version, operating system, and hardware.
- The target and runtime being used, such as LLVM, CUDA, Vulkan, or RPC.
- The relevant build configuration from ``config.cmake``.
- A minimal script, model, input shape, or IR module that reproduces the
  failure.
- The full error message, including both Python and C++ stack traces
  when present.

Developer Notes
---------------

For guidance on raising typed errors from TVM code, see
:ref:`error-handling-guide`.  That guide covers when to use specific
error types, how C++ error prefixes map to Python exceptions, and how
``TVM_FFI_ICHECK`` interacts with TVM's error handling.